There are three main problems associated with the deployment of sensors in harsh environments. Firstly, there are the practical difficulties in getting the sensor to the correct position in the first instance and then, possibly, retrieving it later. Secondly, either the sensor must have a means of storing information, or it must have a means of communicating between the sensor itself and the information processing system. Thirdly, the sensor must be robust enough, not only to take the rigours of deployment, but also be able to function successfully for significant periods of time under harsh conditions. These three aspects are of particular importance in the oil extraction industry. The measurement of pressure at the bottom of an oil well is important for the efficient extraction of the oil reserves. The industry takes two different approaches. In the one case, a measurement system is lowered down the production tube of the well to take and record measurements for a short period before being returned to the surface. Although convenient for use with existing wells and only requiring short term stability of calibration, this approach gives limited information and interferes with the production of oil. In the other case, a measurement system is permanently installed during the construction of the oil well. This has the advantage of giving continuous measurements without interfering with oil production but places very severe requirements on the measurement stability of the sensor and its ability to withstand the high pressures and temperatures in the well for many years. Should such a sensor fail, or doubts be cast upon its accuracy, then the current practice would be to abandon it since it would be too expensive to replace. The permanent installation of a measurement system at the bottom of the oil well also requires significant technical problems to be solved in transferring information via metal or optical fiber cables, or radio links, up to the surface.
The present invention describes a pressure sensor which may be either temporarily or permanently deployed in a convenient fashion, using existing technology familiar to industries such as the oil industry.